1. Field of the Invention
The present invention concerns an artificial hair comprising a fibrous poly-.alpha.-amino acid derivative or a polyamino acid urethane fiber carrying amino groups and mercapto or disulfide groups on the side chains of the polymer.
2. Description of the Prior Art
Poly-.alpha.-amino acids are similar, though they are synthetic polymers, to proteins in view of the chemical structure and have been studied long since as a model of in living body polymers. Further, studies have also been made for their application uses such as artificial skins, enzyme immobilization carriers, piezoelectric elements and cosmetics, in addition to the use of them as a substitute for generally used natural protein such as artificial leather and silk (refer to "Polyamino Acid-Application and Prospect", published, 1974 from Kodansha Co.).
A study has also been made for obtaining various functions from polyacidic amino acid .omega.-esters by converting pendant ester portions thereof through the reaction of ester-exchange or amidation (Journal of Polymer Science: Part C, Polymer Letters, 27, 399 (1989)). As its application example, there has been proposed an artificial hair that can be permed like that human hair starting from a poly-.alpha.-amino acid carrying mercapto or disulfide groups on the side chain (refer to Japanese Patent Laid-Open Sho 63-191829).
However, the poly-.alpha.-amino acid generally has a poor dyeability and it requires extremely complicate and troublesome dyeing steps for the artificial hair of setting by the combination of dyes at present in order to cope with various colors of human hair, which is disadvantageous in view of the cost as well.
Accordingly, a poly-.alpha.-amino acid carrying pendant amino groups and mercapto or disulfide groups and having a plurality of functions has been demanded as a material for the artificial hair.
Various natural protein fibers are identical to poly-.alpha.-amino acids in that they comprise proteins and are composed of various kinds of amino acids, but the natural protein fibers have an extremely complicate fine structure attributable to their constitution comprising various kinds of amino acids. Therefore, feeling and soft and flexible touch of the natural protein fibers can not be attained satisfactorily with synthetic fibers simply composed only of the poly-.alpha.-amino acid. Namely, the a poly-.alpha.-amino acid fiber is rigid and stiff in the feeling as compared with the natural protein fiber to give a problem, for example, in that feeling upon touch is unnatural when it is used as an artificial hair, different from that of the human hair and it can not be brushed smoothly. It is, therefore, demanded for a synthetic fiber which is mainly composed of a poly-.alpha.-amino acid and has a more natural and soft and flexible feeling and is excellent in the brushing property or the like.